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Characterization of polyphenol oxidase from Uapaca kirkiana fruit
Author(s) -
Muchuweti Maud,
Mupure Chipo H,
Ndhlala Ashwell R,
Kasiyamhuru Abisha
Publication year - 2005
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.2329
Subject(s) - polyphenol oxidase , sodium azide , chemistry , pulp (tooth) , sodium metabisulfite , citric acid , catechol oxidase , sodium hypochlorite , laccase , banana peel , food science , chromatography , enzyme , biochemistry , organic chemistry , peroxidase , medicine , pathology
Polyphenol oxidase (PPO), the enzyme responsible for the postharvest spoilage of fruits, was extracted and purified from Uapaca kirkiana peel and pulp by ammonium sulfate precipitation and dialysis. Further purification of peel PPO was carried out by gel filtration chromatography. Optimum pH values were 7 and 8 for peel and pulp PPO, respectively. The optimum temperatures for peel and pulp PPO were 45 and 35 °C, respectively. Inhibition studies of the PPO enzyme were performed using citric acid, sodium azide, sodium metabisulfite and thiourea. The most effective inhibitors were sodium azide and citric acid for both peel and pulp PPO. V max and K m values were 13.63 units min −1 and 4.923 mmol L −1 , respectively, for peel PPO and 14.03 units min −1 and 5.43 mmol L −1 , respectively, for pulp PPO. Three isoenzymes of Uapaca kirkiana PPO were detected by polyacrylamide gel electrophoresis. One of the isoenzymes could be identified as having a molecular weight of 26 625 Da. Copyright © 2005 Society of Chemical Industry